Root system size response of bzh semi-dwarf oilseed rape hybrids to different nitrogen levels in the field.

BACKGROUND AND AIMS: In oilseed rape (Brassica napus) semi-dwarf hybrid varieties from crosses between bzh dwarf and normal-type lines are of increasing interest. They have improved nitrogen (N) uptake, N-utilization and N-use efficiency compared to normal types. This study aimed to elucidate whether these N-related effects can be explained by the bzh shoot growth-type alone or also by differences in root traits. METHODS: Root system size was measured using root electrical capacitance (EC) in field trials with two N levels in two sets of genotypes segregating for the bzh-locus: (1) 108 doubled haploid (DH) test hybrids in two seasons, 2010-2012, and (2) 16 near-isogenic hybrids in the 2016-17 season. Quantitative trait loci (QTL) for root EC were estimated in DH test hybrids. Seedling root architecture parameters were monitored in vitro. KEY RESULTS: In vitro root growth showed a higher root: shoot ratio in bzh semi-dwarf hybrids. Root EC in field trials was higher at high N supply than at zero N fertilization. In most trials semi-dwarf hybrids had higher EC than normal-type hybrids, but they reduced root EC in response to N limitation more than normal types. Root EC was more heritable at the end of flowering (h2 = 0.73) than at the beginning of flowering (h2 = 0.36) in near-isogenic hybrids and had a lower heritability in trials of DH test hybrids (h2 = 0.27). A QTL for root EC in the genomic region of the bzh-locus on linkage group A06 was significant at zero N fertilization. CONCLUSIONS: Root EC proved to be a meaningful method in oilseed rape breeding programmes targeting root system size. The greater reduction of semi-dwarf root EC compared to the normal type under low N supply with simultaneous increase in N efficiency implies that in roots it is not a question of 'the more the merrier' and that the bzh root system reacts highly economically when N is scarce.

DArT, SNP, and SSR analyses of genetic diversity in Lolium perenne L. using bulk sampling.

BACKGROUND: Lolium perenne L. is the most important forage grass species in temperate regions. It is also considered as a sustainable source of biomass for energy production. However, improvement in biomass yield has been limited by comparison with other major crops. More efficient utilisation of genetic resources and improved breeding schemes are required to advance L. perenne breeding. In an attempt to elucidate the extent of genetic diversity in L. perenne, 1384 DArT, 182 SNP and 48 SSR markers were applied to 297 accessions (Set I) contributed by three German breeding companies and the IPK Genebank. Due to the heterogeneous nature of Lolium accessions, bulk samples were used. Apart from germplasm set I, additional set II and set III was used to determine the reproducibility of marker system and judge the feasibility of bulk strategy in this study. RESULTS: By assessing different bulk sizes, 24 individuals per sample were shown to be a representative number of plants to discriminate different accessions. Among the 297 accessions, all marker types revealed a high polymorphism rate; 1.99, 2.00 and 8.19 alleles, were obtained per locus on average using DArTs, SNPs and SSRs, respectively. The Jaccard distance for DArT markers ranged from 0.00 to 0.73, the Modified Roger's distance (MRD) for SNP markers ranged from 0.03 to 0.52, and for SSR markers from 0.26 to 0.76. Gene diversity for dominant DArT and co-dominant SNP and SSR markers was found to be 0.26, 0.32 and 0.45, respectively. DArT markers showed the highest consistency and reproducibility. CONCLUSION: The resulting data were evaluated using a number of different classification methods, but none of the methods showed a clear differentiation into distinct genetic pools. With regard to hybrid breeding, this will possibly impede substantial progress towards increased biomass yields of L. perenne by utilising heterosis.

Mapping of QTL for the seed storage proteins cruciferin and napin in a winter oilseed rape doubled haploid population and their inheritance in relation to other seed traits.

KEY MESSAGE: Cruciferin (cru) and napin (nap) were negatively correlated and the cru/nap ratio was closely negative correlated with glucosinolate content indicating a link between the two biosynthetic pathways. Canola-type oilseed rape (Brassica napus L.) is an economically important oilseed crop in temperate zones. Apart from the oil, the canola protein shows potential as a value-added food and nutraceutical ingredient. The two major storage protein groups occurring in oilseed rape are the 2 S napins and 12 S cruciferins. The aim of the present study was to analyse the genetic variation and the inheritance of napin and cruciferin content of the seed protein in the winter oilseed rape doubled haploid population Express 617 × R53 and to determine correlations to other seed traits. Seed samples were obtained from field experiments performed in 2 years at two locations with two replicates in Germany. A previously developed molecular marker map of the DH population was used to map quantitative trait loci (QTL) of the relevant traits. The results indicated highly significant effects of the year and the genotype on napin and cruciferin content as well as on the ratio of cruciferin to napin. Heritabilities were comparatively high with 0.79 for napin and 0.77 for cruciferin. Napin and cruciferin showed a significant negative correlation (-0.36**) and a close negative correlation of the cru/nap ratio to glucosinolate content was observed (-0.81**). Three QTL for napin and two QTL for cruciferin were detected, together explaining 47 and 35 % of the phenotypic variance. A major QTL for glucosinolate content was detected on linkage group N19 whose confidence interval overlapped with QTL for napin and cruciferin content. Results indicate a relationship between seed protein composition and glucosinolate content.

Resynthesized lines from domesticated and wild Brassica taxa and their hybrids with B. napus L.: genetic diversity and hybrid yield.

Resynthesized (Resyn) Brassica napus L. can be used to broaden the genetic diversity and to develop a heterotic genepool for rapeseed hybrid breeding. Domesticated vegetable types are usually employed as B. oleracea parents. We sought to evaluate the potential of wild species as parents for Resyn lines. Fifteen Resyn lines were derived by crossing wild B. oleracea ssp. oleracea and oilseed B. rapa, and 29 Resyn lines were generated from 10 wild Brassica species (B. bourgaei, B. cretica, B. incana, B. insularis, B. hilarionis, B. macrocarpa, B. montana, B. rupestris, B. taurica, B. villosa). Genetic distances were analyzed with AFLP markers for 71 Resyn lines from wild and domesticated B. oleracea, and compared with 55 winter, spring, vegetable, and Asian B. napus genotypes. The genetic distances clearly showed that Resyn lines with wild species provide a genetic diversity absent from the breeding material or Resyn lines from domesticated species. Forty-two Resyn lines were crossed with one or two winter oilseed rape testers, resulting in 64 hybrids that were grown in one year and four locations in Germany and France. The correlation between hybrid yield and genetic distance was slightly negative (r = -0.29). Most of the hybrids with Resyn lines from wild B. oleracea were lower in yield than hybrids with Resyn lines from domesticated B. oleracea. It is promising that Resyn lines descending from unselected wild B. oleracea accessions produced high-yielding hybrids when crossed with adapted genotypes: these Resyn lines would be suited to develop heterotic pools in hybrid breeding.

Mapping of QTL for seed dormancy in a winter oilseed rape doubled haploid population.

Following winter oilseed rape cultivation, considerable numbers of volunteer oilseed rape plants may occur in subsequent years in following crops. The appearance of volunteer oilseed rape plants is based on the capability of the seeds to become secondary dormant and to survive in this stage for many years in the soil. Genetic reduction of secondary seed dormancy in oilseed rape could provide a means to reduce the frequency of volunteer plants and especially the dispersal of transgenic oilseed rape. The objective of the present study was to analyse the inheritance of primary and secondary seed dormancy in a winter oilseed rape doubled haploid population derived from the cross Express 617 × R53 and to study correlations to other seed traits. Field experiments were performed in Germany for 2 years at two locations with two replicates. Seeds harvested from open pollinated plants were used for all analyses, including a laboratory test for seed dormancy. A previously developed molecular marker map of the doubled haploid population was used to map QTL of the relevant traits. For primary, secondary and total seed dormancy, the results showed significant effects of the genotypes and their interactions, with years and locations. Two, four and five QTL were detected for primary, secondary and total seed dormancy which explained 19, 35 and 42 % of the phenotypic variance, respectively. Results show that secondary seed dormancy is a heritable trait and that selection for low secondary seed dormancy is possible.

Genetic factors inherited from both diploid parents interact to affect genome stability and fertility in resynthesized allotetraploid Brassica napus.

Established allopolyploids are known to be genomically stable and fertile. However, in contrast, most newly resynthesized allopolyploids are infertile and meiotically unstable. Identifying the genetic factors responsible for genome stability in newly formed allopolyploid is key to understanding how 2 genomes come together to form a species. One hypothesis is that established allopolyploids may have inherited specific alleles from their diploid progenitors which conferred meiotic stability. Resynthesized Brassica napus lines are often unstable and infertile, unlike B. napus cultivars. We tested this hypothesis by characterizing 41 resynthesized B. napus lines produced by crosses between 8 Brassica rapa and 8 Brassica oleracea lines for copy number variation resulting from nonhomologous recombination events and fertility. We resequenced 8 B. rapa and 5 B. oleracea parent accessions and analyzed 19 resynthesized lines for allelic variation in a list of meiosis gene homologs. SNP genotyping was performed using the Illumina Infinium Brassica 60K array for 3 individuals per line. Self-pollinated seed set and genome stability (number of copy number variants) were significantly affected by the interaction between both B. rapa and B. oleracea parental genotypes. We identified 13 putative meiosis gene candidates which were significantly associated with frequency of copy number variants and which contained putatively harmful mutations in meiosis gene haplotypes for further investigation. Our results support the hypothesis that allelic variants inherited from parental genotypes affect genome stability and fertility in resynthesized rapeseed.

Extending the rapeseed gene pool with resynthesized Brassica napus II: Heterosis.

Hybrid breeding relies on the combination of parents from two differing heterotic groups. However, the genetic diversity in adapted oilseed rape breeding material is rather limited. Therefore, the use of resynthesized Brassica napus as a distant gene pool was investigated. Hybrids were derived from crosses between 44 resynthesized lines with a diverse genetic background and two male sterile winter oilseed rape tester lines. The hybrids were evaluated together with their parents and check cultivars in 2 years and five locations in Germany. Yield, plant height, seed oil, and protein content were monitored, and genetic distances were estimated with molecular markers (127 polymorphic RFLP fragments). Resynthesized lines varied in yield between 40.9 dt/ha and 21.5 dt/ha, or between 85.1 and 44.6% of check cultivar yields. Relative to check cultivars, hybrids varied from 91.6 to 116.6% in yield and from 94.5 to 103.3% in seed oil content. Mid-parent heterosis varied from -3.5 to 47.2% for yield. The genetic distance of parental lines was not significantly correlated with heterosis or hybrid yield. Although resynthesized lines do not meet the elite rapeseed standards, they are a valuable source for hybrid breeding due to their large distance from present breeding material and their high heterosis when combined with European winter oilseed rape.

Improved Estimation of Oil, Linoleic and Oleic Acid and Seed Hull Fractions in Safflower by NIRS.

Near-infrared reflectance spectroscopy (NIRS) of intact seeds allows the non-destructive estimation of seed quality parameters which is highly desirable in plant breeding. Together with yield, oil content and quality, a main aim in safflower (Carthamus tinctorius L.) breeding is the selection of genotypes with a low percentage of empty seeds even under cooler climates. We developed NIRS calibrations for seed oil content, oleic and linoleic acid content, the seed hull fraction and the percentage of empty seeds using seed meal and intact seeds. For the different calibrations 108-534 samples from a safflower breeding program with lines adapted to German conditions, were analyzed with reference analyses (Soxhlet, gas chromatography), and scanned by NIRS as intact seeds and seed meal. Calibration equations were developed and tested through cross validation. The coefficient of determination of the calibration (R(2)) for intact seeds ranged from 0.91(oil content), 0.90 (seed hull fraction), 0.84 (empty seeds), 0.73 (linoleic acid) to 0.68 (oleic acid). The coefficient of determination of the cross validation was higher for seed meal than for intact seeds except for the parameter seed hull fraction. The results show that NIRS calibrations are applicable in safflower breeding programs for a fast screening.

Extent and structure of linkage disequilibrium in canola quality winter rapeseed (Brassica napus L.).

Linkage disequilibrium was investigated in canola quality winter rapeseed to analyze (1) the prospects for whole-genome association analyses and (2) the impact of the recent breeding history of rapeseed on linkage disequilibrium. A total of 845 mapped AFLP markers with allele frequencies >or=0.1 were used for the analysis of linkage disequilibrium in a population of 85 canola quality winter rapeseed genotypes. A low overall level of linkage disequilibrium was found with a mean r (2) of only 0.027 over all 356,590 possible marker pairs. At a significance threshold of P = 2.8 x 10(-7), which was derived by a Bonferroni correction from a global alpha-level of 0.1, only 0.78% of the marker pairs were in significant linkage disequilibrium. Among physically linked marker pairs, the level of linkage disequilibrium was about five times higher with more than 10% of marker pairs in significant linkage disequilibrium. Linkage disequilibrium decayed rapidly with distance between linked markers with high levels of linkage disequilibrium extending only for about 2 cM. Owing to the rapid decay of linkage disequilibrium with distance association analyses in canola quality rapeseed will have a significantly higher resolution than QTL analyses in segregating populations by interval mapping, but much larger number of markers will be necessary to cover the whole genome. A major impact of the recent breeding history of rapeseed on linkage disequilibrium could not be observed.

Association mapping for phenological, morphological, and quality traits in canola quality winter rapeseed (Brassica napus L.).

QTL mapping by association analysis has recently gained interest in plant breeding research as an alternative to QTL mapping in segregating populations from biparental crosses. In a first experiment on whole-genome association analysis in rapeseed, 684 mapped AFLP markers were tested for association with 14 traits in a set of 84 canola quality winter rapeseed cultivars. For association analysis a general linear model was used. By testing significance of marker-trait associations against a false discovery rate of 0.2, between 1 and 34 associated markers were found for 10 of the 14 traits. Taking into account linkage disequilibrium between the significant markers, these markers represent between 1 and 22 putative QTL for the respective traits. The minimum phenotypic variance explained by the QTL for the different traits ranged from 15% to 53%. A subset of 27 markers were significantly associated with two or more traits. These markers were predominantly shared between traits that were significantly correlated at the phenotypic level. The results show clearly that in rapeseed, QTL mapping by association analysis is a viable alternative to QTL mapping in segregating populations.

Genetic analysis of heterosis for yield and yield components in rapeseed (Brassica napus L.) by quantitative trait locus mapping.

The main objective in this research was the genetic analysis of heterosis in rapeseed at the QTL level. A linkage map comprising 235 SSR and 144 AFLP markers covering 2045 cM was constructed in a doubled-haploid population from a cross between the cultivar "Express" and the resynthesized line "R53." In field experiments at four locations in Germany 250 doubled-haploid (DH) lines and their corresponding testcrosses with Express were evaluated for grain yield and three yield components. The heterosis ranged from 30% for grain yield to 0.7% for kernel weight. QTL were mapped using three different data sets, allowing the estimation of additive and dominance effects as well as digenic epistatic interactions. In total, 33 QTL were detected, of which 10 showed significant dominance effects. For grain yield, mainly complete dominance or overdominance was observed, whereas the other traits showed mainly partial dominance. A large number of epistatic interactions were detected. It was concluded that epistasis together with all levels of dominance from partial to overdominance is responsible for the expression of heterosis in rapeseed.

Effect of crop improvement on genetic diversity in oilseed Brassica rapa (turnip-rape) cultivars, detected by SSR markers.

With the improvement of seed quality, Brassica rapa oilseed germplasm went through 2 major breeding bottlenecks during the introgression of genes for zero erucic acid content and low glucosinolate content, respectively. This study investigates the impact of these bottlenecks on the genetic diversity in European winter B. rapa by comparing 3 open-pollinated cultivars, each representing a different breeding period. Diversity was estimated on 32 plants per cultivar, with 16 simple sequence repeat (SSR) markers covering each of the B. rapa linkage groups. There was no significant loss of genetic diversity over the 3 cultivars as indicated by allele number (ranging from 59 to 55), mean allele number (from 3.68 to 3.50), Shannon information index (from 0.94 to 0.87) and expected heterozygosity (from 0.53 to 0.48). About 83% of the total variation was attributed to within-cultivar variation, and the remaining 17% to between-cultivar variation by analysis of molecular variance (AMOVA). Individual plants were separated into the 3 cultivars by principal coordinate analysis (PCoA). In conclusion, genetic diversity within cultivars was high and quality breeding in B. rapa did not significantly reduce the genetic diversity of B. rapa winter cultivars, so there is no risk of decline in performance due to quality improvement.

Evaluation of nine genotypes of oilseed rape (Brassica napus L.) for larval infestation and performance of rape stem weevil (Ceutorhynchus napi Gyll.).

The rape stem weevil, Ceutorhynchus napi Gyll., is a serious pest of winter oilseed rape (Brassica napus L.) crops in Europe causing severe yield loss. In currently used oilseed rape cultivars no resistance to C. napi has been identified. Resynthesized lines of B. napus have potential to broaden the genetic variability and may improve resistance to insect pests. In this study, the susceptibility to C. napi of three cultivars, one breeding line and five resynthesized lines of oilseed rape was compared in a semi-field plot experiment under multi-choice conditions. Plant acceptance for oviposition was estimated by counting the number of C. napi larvae in stems. The larval instar index and the dry body mass were assessed as indicators of larval performance. The extent of larval feeding within stems was determined by the stem injury coefficient. Morphological stem traits and stem contents of glucosinolates were assessed as potential mediators of resistance. The resynthesized line S30 had significantly fewer larvae than the cultivars Express617 and Visby and the resynthesized lines L122 and L16. The low level of larval infestation in S30 was associated with a low larval instar and stem injury index. Low numbers of larvae were not correlated with the length or diameter of stems, and the level of stem glucosinolates. As indicated by the low larval infestation and slow larval development the resistance of S30 to C. napi is based on both antixenotic and antibiotic properties of the genotypes. The resynthesized line S30 should therefore be introduced into B. napus breeding programs to enhance resistance against C. napi.

QTL of three agronomically important traits and their interactions with environment in a European x Chinese rapeseed population.

A rapeseed population consisted of 282 doubled haploid (DH) lines derived from a cross between a European vality "Sallux" and a Chinese inbred line "Gaoyou" was planted in 4 locations, 2 in Xi'an and Hangzhou, China, and 2 in Goettingen, Germany. Field experiments were carried out to obtain agronomically phenotypic data from above four environments. A linkage map including 125 SSR-markers was constructed and QTL analyses was performed using mixed model approach to detect QTLs showing additive (a), epistasis (aa) as well as their interactions with environments (QE) for three important agronomic traits: plant height, flowering time and maturity. The results demonstrated that each trait was controlled by several QTLs with additive effect and a number of QTLs with epistatic and QE interaction effects. Plant height was controlled by many QTLs (12 loci with a or combined ae, 5 loci with ae). Additive effects were predominant,totally explained 75% of the phenotypic variation and often combined with digenic epistasis. Of 12 main QTLs, 9 showed Gaoyou alleles decreasing plant height. Most of QTLs with QE effects showed ecologically favourable alleles in diverse regions. Five of 7 ae loci showed Gaoyou alleles in Hangzhou and all the ae loci but one had Sollux alleles in two locations of Germany increasing plant height. The digenic epistatic main effect accounted for one third of total additive main effects. In this study,we discovered 7 and 8 loci having significant additive main effects upon flowering time and maturity, respectively. Of them, early flowering and maturity alleles were respectively 6 and 5 derived from Chinese parent Gaoyou. All these QTLs together accounted for around 60% of the phenotypic variation for each trait. Significant ae interactions were detected for flowering time and maturity and parental alleles showed almost evenly dispersal at all environments. Three of 8 main QTLs for maturity were located at similar or identical positions as QTLs for flowering time, which confirmed the close correlation between these two traits. Two QTLs for plant height on linkage groups N14-1 and 19 were located at similar positions as QTL for flowering time and as already known QTLs for oil content. Selection for reduced plant height and early flowering might reduce oil content. Digenic epistatic QTLs both for flowering time and maturity were detected but much less important than QTLs with additive effects.

Biomass yield and heterosis of crosses within and between European winter cultivars of turnip rape (Brassica rapa L.).

Because of its high growth rate at low temperatures in early spring, there is renewed interest in Brassica rapa as a winter crop for biomass production in Europe. The available cultivars are not developed for this purpose however. An approach for breeding bioenergy cultivars of B. rapa could be to establish populations from two or more different cultivars with high combining ability. The objective of this study was to evaluate the heterosis for biomass yield in the European winter B. rapa genepool. The genetic variation and heterosis of the biomass parameters: dry matter content, fresh and dry biomass yields were investigated in three cultivars representing different eras of breeding by comparing full-sibs-within and full-sibs-between the cultivars. Field trials were performed at two locations in Germany in 2005-2006. Mean mid-parent heterosis was low with 2.5% in fresh and 3.0% in dry biomass yield in full-sibs-between cultivars. Mean values of individual crosses revealed a higher variation in mid-parent heterosis ranging from 14.6% to -7.5% in fresh biomass yield and from 19.7% to -12.7% in dry biomass yield. The low heterosis observed in hybrids between European winter cultivars can be explained by the low genetic variation between these cultivars as shown earlier with molecular markers. In conclusion, a B. rapa breeding program for biomass production in Europe should not only use European genetic resources, but should also utilize the much wider worldwide variation in this species.

A new near-infrared reflectance spectroscopy method for high-throughput analysis of oleic acid and linolenic acid content of single seeds in oilseed rape (Brassica napus L.).

The development of oilseed rape cultivars with a high content of oleic acid (18:1) and a low content of linolenic acid (18:3) in the seed oil is an important breeding aim. Oil of this quality is increasingly being sought by the food and the oleochemical industry. Since the oil quality is determined by the genotype of the seed, a selection can be performed among single seeds of segregating populations. For this purpose a high-throughput Near-Infrared Reflectance Spectroscopy (NIRS) method using an automated sample presentation unit for single seeds of oilseed rape and a spectrometer equipped with a photodiode array detector was developed. Single-seed analyses have been accomplished with a throughput of up to 800 seeds per hour. Seeds from segregating populations of different origin were analyzed by NIRS and gas chromatography. Calibration equations were developed and validated applying the Modified Partial Least Square regression (MPLS) and LOCAL procedure. In three independent validations, standard errors of prediction corrected for bias between 2.7% and 3.7% for oleic acid and 1.2% and 1.8% for linolenic acid were determined using MPLS. Similar results were obtained applying the LOCAL procedure. The results show that the new high-throughput method can be applied to predict the oleic acid and linolenic acid content of single seeds of oilseed rape.

Increasing erucic acid content through combination of endogenous low polyunsaturated fatty acids alleles with Ld-LPAAT + Bn-fae1 transgenes in rapeseed (Brassica napus L.).

High erucic acid rapeseed (HEAR) oil is of interest for industrial purposes because erucic acid (22:1) and its derivatives are important renewable raw materials for the oleochemical industry. Currently available cultivars contain only about 50% erucic acid in the seed oil. A substantial increase in erucic acid content would significantly reduce processing costs and could increase market prospects of HEAR oil. It has been proposed that erucic acid content in rapeseed is limited because of insufficient fatty acid elongation, lack of insertion of erucic acid into the central sn-2 position of the triaclyglycerol backbone and due to competitive desaturation of the precursor oleic acid (18:1) to linoleic acid (18:2). The objective of the present study was to increase erucic content of HEAR winter rapeseed through over expression of the rapeseed fatty acid elongase gene (fae1) in combination with expression of the lysophosphatidic acid acyltransferase gene from Limnanthes douglasii (Ld-LPAAT), which enables insertion of erucic acid into the sn-2 glycerol position. Furthermore, mutant alleles for low contents of polyunsaturated fatty acids (18:2 + 18:3) were combined with the transgenic material. Selected transgenic lines showed up to 63% erucic acid in the seed oil in comparison to a mean of 54% erucic acid of segregating non-transgenic HEAR plants. Amongst 220 F(2) plants derived from the cross between a transgenic HEAR line and a non-transgenic HEAR line with a low content of polyunsaturated fatty acids, recombinant F(2) plants were identified with an erucic acid content of up to 72% and a polyunsaturated fatty acid content as low as 6%. Regression analysis revealed that a reduction of 10% in polyunsaturated fatty acids content led to a 6.5% increase in erucic acid content. Results from selected F(2) plants were confirmed in the next generation by analysing F(4) seeds harvested from five F(3) plants per selected F(2) plant. F(3) lines contained up to 72% erucic acid and as little as 4% polyunsaturated fatty acids content in the seed oil. The 72% erucic acid content of rapeseed oil achieved in the present study represents a major breakthrough in breeding high erucic acid rapeseed.

QTL for phytosterol and sinapate ester content in Brassica napus L. collocate with the two erucic acid genes.

Improving oil and protein quality for food and feed purposes is an important goal in rapeseed (Brassica napus L.) breeding programs. Rapeseed contains phytosterols, used to enrich food products, and sinapate esters, which are limiting the utilization of rapeseed proteins in the feed industry. Increasing the phytosterol content of oil and lowering sinapate ester content of meal could increase the value of the oilseed rape crop. The objective of the present study was to identify quantitative trait loci (QTL) for phytosterol and sinapate ester content in a winter rapeseed population of 148 doubled haploid lines, previously found to have a large variation for these two traits. This population also segregated for the two erucic acid genes. A close negative correlation was found between erucic acid and phytosterol content (Spearman's rank correlation, r(s) = -0.80**). For total phytosterol content, three QTL were detected, explaining 60% of the genetic variance. The two QTL with the strongest additive effects were mapped on linkage groups N8 and N13 within the confidence intervals of the two erucic acid genes. For sinapate ester content four QTL were detected, explaining 53% of the genetic variance. Again, a close negative correlation was found between erucic acid and sinapate ester content (r(s) = -0.66**) and the QTL with the strongest additive effects mapped on linkage groups N8 and N13 within the confidence intervals of the two erucic acid genes. The results suggests, that there is a pleiotropic effect of the two erucic acid genes on phytosterol and sinapate ester content; the effect of the alleles for low erucic acid content is to increase phytosterol and sinapate ester content. Possible reasons for this are discussed based on known biosynthetic pathways.

Comparison of phenotypic and molecular distances to predict heterosis and F1 performance in Ethiopian mustard (Brassica carinata A. Braun).

Predicting heterosis and F1 performance from the parental generation could largely enhance the efficiency of breeding hybrid or synthetic cultivars. This study was undertaken to determine the relationship between parental distances estimated from phenotypic traits or molecular markers with heterosis, F1 performance and general combining ability (GCA) in Ethiopian mustard (Brassica carinata). Nine inbred lines representing seven different geographic regions of Ethiopia were crossed in half-diallel. The nine parents along with their 36 F1s were evaluated in a replicated field trail at three locations in Ethiopia. Distances among the parents were calculated from 14 phenotypic traits (Euclidean distance, ED) and 182 random amplified polymorphic DNA (RAPD) markers (Jaccard's distances, JD), and correlated with heterosis, F1 performance and GCA sum of parents (GCAsum). The correlation between phenotypic and molecular distances was low (r=0.34, P< or =0.05). Parents with low molecular distance also had low phenotypic distance, but parents with high molecular distance had either high, intermediate or low phenotypic distance. Phenotypic distance was highly significantly correlated with mid-parent heterosis (r=0.53), F1 performance (r=0.61) and GCA (r=0.79) for seed yield. Phenotypic distance was also positively correlated with (1) heterosis, F1 performance and GCA for plant height and seeds plant(-1), (2) heterosis for number of pods plant(-1), and (3) F1 performance for 1,000 seed weight. Molecular distance was correlated with GCAsum (r=0.36, P< or =0.05) but not significantly with heterosis and F1 performance for seed yield. For each parent a mean distance was calculated by averaging the distances to the eight other parents. Likewise, mean heterosis was estimated by averaging the heterosis obtained when each parent is crossed with the other eight. For seed yield, both mean ED and JD were significantly correlated with GCA (r=0.90, P< or =0.01 for ED and r=0.68, P< or =0.05 for JD) and mean heterosis (r=0.79, P< or =0.05 for ED and r=0.77, P< or =0.05 for JD). In conclusion, parental distances estimated from phenotypic traits better predicted heterosis, F1 performance and GCA than distances estimated from RAPD markers.

Conditional QTL mapping of oil content in rapeseed with respect to protein content and traits related to plant development and grain yield.

Oil content in rapeseed (Brassica napus L.) is generally regarded as a character with high heritability that is negatively correlated with protein content and influenced by plant developmental and yield related traits. To evaluate possible genetic interrelationships between these traits and oil content, QTL for oil content were mapped using data on oil content and on oil content conditioned on the putatively interrelated traits. Phenotypic data were evaluated in a segregating doubled haploid population of 282 lines derived from the F(1) of a cross between the old German cultivar Sollux and the Chinese cultivar Gaoyou. The material was tested at four locations, two each in Germany and in China. QTLMapper version 1.0 was used for mapping unconditional and conditional QTL with additive (a) and locus pairs with additive x additive epistatic (aa) effects. Clear evidence was found for a strong genetic relationship between oil and protein content. Six QTL and nine epistatic locus pairs were found, which had pleiotropic effects on both traits. Nevertheless, two QTL were also identified, which control oil content independent from protein content and which could be used in practical breeding programs to increase oil content without affecting seed protein content. In addition, six additional QTL with small effects were only identified in the conditional mapping. Some evidence was apparent for a genetic interrelationship between oil content and the number of seeds per silique but no evidence was found for a genetic relationship between oil content and flowering time, grain filling period or single seed weight. The results indicate that for closely correlated traits conditional QTL mapping can be used to dissect the genetic interrelationship between two traits at the level of individual QTL. Furthermore, conditional QTL mapping can reveal additional QTL with small effects that are undetectable in unconditional mapping.